Support is requested for a Keystone Symposia meeting entitled Noncoding RNAs in Development and Cancer, organized by Joshua T. Mendell, Phillip A. Sharp, Judy Lieberman and Howard Y. Chang, which will be held in Vancouver, British Columbia, Canada from January 20 - 25, 2013. A recurrent principle in cancer biology is the co-option of pathways that function during development to promote aberrant tumor cell behavior. This principle clearly applies to the roles of noncoding RNAs in cancer. Examples of noncoding RNAs that modify tumor phenotypes include the microRNA (miRNA) let-7, a key regulator of developmental timing in C. elegans, and the miR-17-92 cluster, which conducts essential regulatory functions during mammalian development. However, we currently have only a rudimentary understanding of how diverse classes of noncoding RNAs function in physiologic and pathophysiologic states. This meeting will bring together experts focused on the roles of noncoding RNAs in development and cancer with the broad goals of 1) illuminating new connections between developmental and cancer pathways controlled by miRNAs and long noncoding RNAs; 2) uncovering novel mechanisms by which developmental and cancer pathways influence noncoding RNA processing and activity; 3) revealing the molecular mechanisms through which miRNAs and long noncoding RNAs function in these pathways; and 4) highlighting how our understanding of noncoding RNA-regulated pathways can be applied in the development of novel therapeutic strategies for cancer and perhaps other diseases. To accomplish these goals, this meeting will bring together experts from disparate fields ranging from organismal- level developmental and cancer biology to biochemical and molecular studies of RNA function to share their newest data and ideas. It is anticipated that the diverse views, approaches, and results presented by participants will foster new lines of investigation and collaborations which will be critical to dissect the myriad functions of noncoding RNAs in health and disease.